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Polymicrobial infections are one of the most common reasons for inflammation of surrounding tissues and failure of implanted biomaterials. Because microorganism adhesion is the first step for biofilm formation, physical–chemical modifications of biomaterials have been proposed to reduce the initial microbial attachment. Thus, the use of superhydrophobic coatings has emerged because of their anti-biofilm properties. However, these coatings on the titanium (Ti) surface have been developed mainly by dual-step surface modification techniques and have not been tested using polymicrobial biofilms. Therefore, we developed a one-step superhydrophobic coating on the Ti surface by using a low-pressure plasma technology to create a biocompatible coating that reduces polymicrobial biofilm adhesion and formation. The superhydrophobic coating on Ti was created by the glow discharge plasma using Ar, O2, and hexamethyldisiloxane gases, and after full physical, chemical, and biological characterizations, we evaluated its properties regarding oral biofilm inhibition. The newly developed coating presented an increased surface roughness and, consequently, superhydrophobicity (contact angle over 150°) and enhanced corrosion resistance (p < 0.05) of the Ti surface. Furthermore, proteomic analysis showed a unique pattern of protein adsorption on the superhydrophobic coating without drastically changing the biologic processes mediated by proteins. Additionally, superhydrophobic treatment did not present a cytotoxic effect on fibroblasts or reduction of proliferation; however, it significantly reduced (≈8-fold change) polymicrobial adhesion (bacterial and fungal) and biofilm formation in vitro. Interestingly, superhydrophobic coating shifted the microbiological profile of biofilms formed in situ in the oral cavity, reducing by up to ≈7 fold pathogens associated with the peri-implant disease. Thus, this new superhydrophobic coating developed by a one-step glow discharge plasma technique is a promising biocompatible strategy to drastically reduce microbial adhesion and biofilm formation on Ti-based biomedical implants.

Oral rehabilitation devices are susceptible to bio-tribocorrosion phenomena in the oral environment due to the synergism of wear, chemical, biochemical, and microbiological processes. This review summarizes the clinical problems and advances obtained based on current scientific evidence as well as the influence of tribological fundamentals, testing methodologies, and protocols in tribocorrosion analyses. The main clinical question related to oral rehabilitation with dental implants is the treatment failure, which is influenced by material degradation. Titanium-based implants are exposed to wear and corrosion challenges in the oral environment since the implantation and along the lifetime service. The titanium (Ti) properties such as structural material, connection design, surface treatments, alloying elements are influencing factors for material behavior. In addition, wear-corrosion factors such as cyclic loads, micromovements, oral biofilm, decontamination methods are also associated with dental implants degradation. These environmental conditions to which dental implants are submitted leads to the release of Ti particles and ions with cytotoxic and harmful effects on peri-implant surrounding tissues. In this context, the current state of the art of bio-tribocorrosion over the last decade has been steadily increasing to understand material degradation. The basic test system used to translate the tribocorrosion phenomena in the oral environment to the bench consists of electrochemical and tribological synergic analysis. The mechanical (applied load, frequency, stroke distance, and number of cycles) and electrochemical (solution composition, concentration of anions, and pH) test conditions are determinants for materials tribocorrosion performance. To overcome the tribocorrosion phenomena some strategies have been used such as alloying elements for Ti-alloys manufacture, surface treatments, and biomolecules immobilization. Further studies need to have the tribocorrosion analyses as the basis for new smart materials development considering the importance of such aspects for the biomaterial clinical behavior. Finally, tribological tests are relevant strategies for understanding the mechanisms of degradation in the oral environment and for providing a way to improve the clinical outcomes of dental implants.

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